A class of industrial problems exists in which a large number of items must be separated, identified, counted and sorted. One example occurs in the textile service industry, wherein soiled garments or linens are returned in large unsorted groups for cleaning and sorting. Present day means for solving this problem cover a broad spectrum. One solution uses manual workers who sequentially sort among the many items, picking single items manually and identifying the items visually. This solution is unsatisfactory because it is both slow and expensive due to the high reliance on manual labor.
There are numerous coding and sorting systems presently available. Many of these industrial problems are not overcome by present systems, such as those employing bar codes or radio frequency identification (RFID). For example, a particularly challenging problem is the sorting of goods which are flexible and therefore may easily distort or shield a code. These items, which range in size from very small to large, are typically presented in distorted orientations and may undergo severe use cycles that can easily damage identification tags.
In addition, bar codes are highly susceptible to degradation through both soiling and wear. Furthermore, due to the precise spatial information required for a bar code (line width and spacing), any warping of the label (almost assured on a fabric substrate) can result in reading rates that are characterized by high rates of error. Finally, bar codes require line-of-sight and (generally) a specific orientation with respect to the detector, both of which are difficult conditions to satisfy under typical large scale laundry conditions.
In contrast, the radio-frequency ID technique does not suffer from the line of sight and soiling problems associated with bar codes. However, RFID remains expensive, both from initial cost and associated maintenance costs, and therefore is normally not economical for the rental textile industry. Furthermore, RFID tags have a tendency to exhibit cross-talk when they are in proximity to one another, which can preclude their use on closely-spaced sorting conveyors.
These are just some of the technological barriers to accurate machine identification and automated counting and sorting. The lack of a viable coding and sorting solutions has resulted in high labor costs, lack of stock control, and reduced profits.
In spite of these disadvantages, these technologies have provided significant benefit to certain applications. Such advances have been witnessed in applications where certain steps have been a rate determining factor. For example, the use of bar codes and RFID has provided for increased speed of identification in high speed coding and sorting systems.
Accordingly, many technologies have arisen to address certain aspects of high throughput coding and sorting applications. Many of the systems presently available rely upon optical properties.
One example is an indicia reader disclosed in U.S. Pat. No. 5,920,056 “Optically-Guided Indicia Reader System for Assisting in Positioning a Parcel on a Conveyor,” Bonnet, issued Jul. 6, 1999. The system disclosed in this patent is limited, however, in that it fails to account for imaging of indicia having an appearance that may be distorted, such as by the wrinkling of the substrate.
Another patent that provides for remote identification of objects is U.S. Pat. No. 3,902,047 “Label Reader with Rotatable Television Scan” Tyler et al., issued Aug. 26, 1975. This system provides for rotation of the orientation of an optically read label by electronic means. However, as with the previous patent, it fails to account for imaging of indicia having an appearance that may be distorted, such as by the wrinkling of the substrate.
Another aspect of coding is presented in the U.S. Pat. No. 3,513,320 “Article Identification System Detecting Plurality of Colors Disposed on Article” Weldon, May 19, 1970. Weldon discloses encoding a number, where various code hues (wavelengths) in a single patch provide a unique signal. Coded signals in a series of patches provide for a message. Weldon further discloses the use of control patches, such as a central spot, that emits only one control hue (wavelength), for providing control of sensors used in readout tasks such as governing positioning of a readout system for addressing indicia comprising successively enclosing zones. As Weldon calls for use in some embodiments of a varied number of hues in each patch, the system may experience decoding problems in some applications, for example, where irregular patch geometries are presented. Accordingly, Weldon appears to require accurately and uniformly pre-positioning the patches on the object; and, in another embodiment, accurate control of the orientation of the substrate to provide for successful imaging (see, for example, the embodiment of FIG. 2a, where a series of parallel narrow areas of varying code hues may comprise a colorant having one or more code hues contained therein). Furthermore, Weldon does not provide for implementation of many existing code schemes, such as bar codes, which incorporate elements having varied features (e.g. size and width), some of the bar codes themselves requiring further improvement.
Thus, a technique that provides for a machine readable marking, where the marking may appear in an irregular or distorted form is needed. Preferably, the technology should offer the ease of use and the low cost associated with bar codes, and yet be more robust and tolerant of harsh or high throughput environments, such as large scale document and package handling facilities.
In U.S. Pat. No.: 5,881,886 “Optically-Based Methods and Apparatus for Sorting Garments and Other Textiles” one of the inventors of this patent application has described various methods and apparatus that also address the problems referred to above.